/**
 * zoneland.net Inc.
 * Copyright (c) 2002-2012 All Rights Reserved.
 */
package com.sanerzone.smscenter.gateway.ums.util;

/**
 * 
 * @author liuzhenxing
 * @version $Id: Base64.java, v 0.1 2012-5-11 下午4:30:04 liuzhenxing Exp $
 */
public class Base64 {
    private static char[] Base64Code   = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K',
            'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b',
            'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
            't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
            '+', '/'                  };

    private static byte[] Base64Decode = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, 62, -1, 63, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,
            -1, -1, -1, 0, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
            17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32,
            33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1,
            -1, -1                    };

    public static String encode(byte[] b) {
        int code = 0;

        StringBuffer sb = new StringBuffer((b.length - 1) / 3 << 6);

        for (int i = 0; i < b.length; ++i) {
            code |= b[i] << 16 - (i % 3 * 8) & 255 << 16 - (i % 3 * 8);
            if ((i % 3 == 2) || (i == b.length - 1)) {
                sb.append(Base64Code[((code & 0xFC0000) >>> 18)]);
                sb.append(Base64Code[((code & 0x3F000) >>> 12)]);
                sb.append(Base64Code[((code & 0xFC0) >>> 6)]);
                sb.append(Base64Code[(code & 0x3F)]);
                code = 0;
            }

        }

        if (b.length % 3 > 0) {
            sb.setCharAt(sb.length() - 1, '=');
        }
        if (b.length % 3 == 1) {
            sb.setCharAt(sb.length() - 2, '=');
        }
        return sb.toString();
    }

    public static byte[] decode(String code) {
        if (code == null) {
            return null;
        }
        int len = code.length();
        if (len % 4 != 0) {
            throw new IllegalArgumentException("Base64 string length must be 4*n");
        }
        if (code.length() == 0) {
            return new byte[0];
        }

        int pad = 0;
        if (code.charAt(len - 1) == '=') {
            ++pad;
        }
        if (code.charAt(len - 2) == '=') {
            ++pad;
        }

        int retLen = len / 4 * 3 - pad;

        byte[] ret = new byte[retLen];

        for (int i = 0; i < len; i += 4) {
            int j = i / 4 * 3;
            char ch1 = code.charAt(i);
            char ch2 = code.charAt(i + 1);
            char ch3 = code.charAt(i + 2);
            char ch4 = code.charAt(i + 3);
            int tmp = Base64Decode[ch1] << 18 | Base64Decode[ch2] << 12 | Base64Decode[ch3] << 6
                      | Base64Decode[ch4];

            ret[j] = (byte) ((tmp & 0xFF0000) >> 16);
            if (i < len - 4) {
                ret[(j + 1)] = (byte) ((tmp & 0xFF00) >> 8);
                ret[(j + 2)] = (byte) (tmp & 0xFF);
            } else {
                if (j + 1 < retLen) {
                    ret[(j + 1)] = (byte) ((tmp & 0xFF00) >> 8);
                }
                if (j + 2 < retLen) {
                    ret[(j + 2)] = (byte) (tmp & 0xFF);
                }
            }
        }
        return ret;
    }

}
